Antenatal betamethasone therapy potentiates nitric oxide-mediated
relaxation of preterm ovine coronary arteries.
Gao, Yuansheng, Haiyan Zhou, and J. Usha Raj.
Department of Pediatrics, Harbor-UCLA Medical Center, University of
California, Los Angeles, School of Medicine, Torrance, CA 90509
APStracts 2:0348H, 1995.
The present study was designed to test the hypothesis that
betamethasone may potentiate nitric oxide-mediated relaxation of
coronary arteries of preterm lambs. Isolated coronary arteries were
obtained from lambs delivered at 128 d gestation. The lambs were
treated with a single dose of betamethasone or saline (I.M.) 48 h
before delivery and were sacrificed after 3 h of ventilation
following delivery. Vessel rings were suspended in organ chambers
filled with modified Krebs-Ringer solution (95% O2-5% CO2, 37 degrees
C) and their isometric tension was recorded. The endothelium
-dependent relaxation induced by bradykinin and calcium ionophore
A23187 was greater in arteries from antenatal betamethasone-treated
lambs than in those from control lambs. The relaxation was abolished
by nitro-L-arginine. Nitric oxide induced a greater relaxation of
vessels of antenatal betamethasone-treated lambs and vessels
preincubated with betamethasone than that of control. Coronary
arteries of control and antenatal betamethasone-treated lambs relaxed
similarly to 8-Bromo-cGMP. Nitric oxide induced an greater increase
in cGMP content of coronary arteries of antenatal betamethasone
-treated lambs than that of arteries of control lambs. Our data
suggest that antenatal betamethasone therapy potentiates nitric
oxide-mediated relaxation of coronary arteries of preterm lambs,
probably by affecting the activity of soluble guanylate cyclase of
vascular smooth muscle cells.
Received 17 January 1995; accepted in final form 4 August 1995.
APS Manuscript Number H39-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.